1. Field of the Invention
The present invention relates to a socket for electrical parts for detachably accommodating and holding an electrical part such as a semiconductor device (called as xe2x80x9cIC packagexe2x80x9d hereinlater), and more particularly, relates to a socket for an electrical part having improved contact pins to be contacted to or separated from terminals of the electrical part.
2. Related Art of the Invention
In a known art, there is provided a socket of the type mentioned above, for example, as disclosed it Japanese Patent Laid-open Publication No. HEI 10-116670, which shows a structure, as shown in FIG. 9, in which a device 3 achieves an electrical connection between a terminal 1a of an IC package as an electrical part and a terminal 2a of a printed circuit board 2 and a contact pin 4 is arranged to a body of the device (socket) 3.
The contact pin 4 shown in FIG. 9 is formed from a conductive plate member with engaging grooves 4a and 4b at both end portions. A support structure is provided by fitting an elastic element 5 to one 4a of the engaging grooves and a hard element 6 to the other one 4b of the engaging grooves.
With reference to FIG. 9, an upper end portion of such contact pin 4 abuts against the terminal 1a of the IC package and a lower end portion thereof abuts against the terminal 2a of the printed circuit board 2 to thereby establish an electrical connection, through the contact pin 4, between the terminal 1a of the IC package 1 and the terminal 2a of the printed circuit board 2.
In such contact pin 4, the engaging groove 4b has relatively long slot shape in the vertical direction, and accordingly, when the IC package 1 is depressed downward, the contact pin 4 may somewhat be rotated and the contacting portion of the contact pin 4 slightly slides on the lower surface of the terminal 1a of the IC package 1, thus achieving wiping effect. Further, such sliding motion will be observed between the contact pin 4 and the terminal 2a of the printed circuit board 2.
However, in such socket of the prior art, the contact pin 4 has a predetermined proper width, but it has a long length extending in an oblique direction, as viewed, so as to provide a rotational structure, and therefore, the contact pin 4 occupies a relatively large location space with respect to the device body 3 and it is difficult to effectively improve a high frequency characteristic of the contact pin 4.
Moreover, in a structure in which the terminals 1a of the IC package 1 are formed to four sides of an IC package having rectangular shape, it is difficult to arrange the contact pins 4, and it is hence difficult to carry out an inspection of such IC package 1.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art described above and to provide a socket for an electrical part such as IC package capable of improving a high frequency characteristic of a contact, i.e. contact pin, disposing the contact pin in a narrow space and suitably carrying out an inspection of the IC package.
This and other objects can be achieved according to the present invention by providing a socket for an electrical part having a socket body in which an electrical part is accommodated and to which a number of contact pins are arranged so as to be contacted to or separated from terminals provided for an electrical part and to thereby establish an electrical connection between a printed circuit board and the terminal of the electrical part,
the contact pin comprising a first contact piece disposed on an electrical part side so as to contact the terminal of the electrical part and a second contact piece disposed on a printed circuit board side so as to contact the printed circuit board, wherein when the first contact piece contacts the terminal of the electrical part and is then pressed, the first contact piece is inclined and a contact end portion of the first contact piece is moved so as to slide with respect to the electrical part.
In preferred embodiments, the first and second contact pieces of the contact pin have central axes offset from each other and when the first contact piece contacts the terminal of the electrical part and is then pressed, the first contact piece is inclined and a contact end portion of the first contact piece is moved so as to slide with respect to the electrical part.
The first contact piece is provided with a contact end portion, offset from the central axis of the first contact piece, having a shape capable of contacting the terminal of the electrical part and when the first contact piece contacts the terminal of the electrical part and is then pressed, the first contact piece is inclined and a contact end portion of the first contact piece is moved so as to slide with respect to the electrical part.
The first contact piece has a circular portion and the second contact piece has a contact receiving portion for receiving and supporting the circular portion of the first contact piece to be movable. The second contact piece is provided with a pair of elastic pieces, as a contact receiving portion, supporting the first contact piece. The elastic pieces have different elastic forces so that when the first contact piece contacts the terminal of the electrical part and is then pressed, the first contact piece is inclined and a contact end portion of the first contact piece is moved so as to slide with respect to the electrical part.
The first and second contact pieces are formed independently to be flat by punching out plate members composed of, for example, a beryllium copper material.
The second contact piece of the contact pin is supported by a cushion member and when the cushion member is elastically deformed, the second contact piece is allowed to be inclined and is returned to a vertical position by an elastic force of the cushion member.
The socket is an IC socket and the electrical part is an IC package of land grid array type.
According to the present invention of the structures mentioned above, the contact pin provided for the socket body of the socket for an electrical part comprises a first contact piece disposed on an electrical part side (electrical part side contact piece) so as to contact the terminal of the electrical part and a second contact piece disposed on a printed circuit board side (printed circuit board side contact piece) so as to contact the printed circuit board, wherein when the first contact piece contacts the terminal of the electrical part and is then pressed, the first contact piece is inclined and a contact end portion of the first contact piece is moved so as to slide with respect to the electrical part. Therefore, an improved wiping effect can be achieved and a high frequency characteristic of the contact pin can be also improved. The contact pins of the structure mentioned above have a reduced space for the location. Moreover, an inspection of an electrical part formed with four terminals at its four sides can be effectively performed.
Furthermore, the electrical part side contact piece can be easily inclined with a simple design change. The contact pressure between the electrical part side contact piece of the contact pin and the printed circuit board side contact piece thereof can be surely maintained by forming the elastic portions for supporting the electrical part side contact piece.
The nature and further characteristic features of the present invention will be made further clear from the following descriptions made with reference to the accompanying drawings.